1. Field of the Invention
This invention relates broadly to medical instruments. More particularly, this invention relates to basket devices for retrieving calculi located in the urological and gastrointestinal ducts. This invention can also be used to retrieve foreign objects from various locations within the mammalian body.
2. State of the Art
Surgical basket instruments are inserted into endoscopes and are typically used to remove calculi in the form of kidney stones, gallstones, biliary stones, and the like from the body without requiring a large incision. The basket instruments generally include a shaft having a resilient basket assembly coupled (for example, via crimping, welding, or soldering) to the distal end thereof, and a sheath (catheter) through which the shaft is axially extendable. The basket assembly is generally formed from resilient strands defining a cage-like enclosure. The basket assembly is radially collapsible to fit within the sheath, but distal movement of the shaft relative to the sheath enables the basket assembly to be moved beyond the distal end of the sheath. A wire, cable, or other mechanism, coupled proximally to the shaft at a handle and distally to the basket, is used to manipulate and expand and contract the extended basket. When the basket is in an expanded state, the basket may be maneuvered to envelop a calculus. The shaft may then be moved relative to the sheath to collapse the basket around the calculus and secure the calculus therein. The entire instrument is then withdrawn from the body of the patient along with the calculus. In addition, baskets may be expanded within a vein and rotated to function as a filter or thrombectomy device.
Several different basket designs are known in the art. For example, U.S. Pat. No. 5,064,428 to Cope et al., U.S. Pat. No. 4,611,594 to Grayhack et al., and U.S. Pat. Nos. 5,496,330 and 5,788,710 both to Bates et al. disclose prior art basket assemblies, and are hereby incorporated by reference herein in their entireties. U.S. Pat. No. 5,176,688 to Narayan et al., discloses an endoscopic basket instrument for use with a multi-bore endoscope having a first bore provided for operating a basket assembly, a second bore provided for a hammer, and a third bore for an optical system, and is hereby incorporated by reference herein in its entirety. U.S. Pat. No. 5,057,114 to Wittich et al. discloses an endoscopic basket instrument having a basket formed from superelastic metallic alloy wires, and is hereby incorporated by reference herein in its entirety.
However, the medical community has not been satisfied with the currently available basket instruments. In particular, with the instruments of the prior art, it is relatively difficult to visualize the surroundings at the distal end of the basket assembly especially when the basket contains a large calculus, adequately steer the instrument through the tortuous urological or gastrointestinal tracts, and adequately surround and capture a large calculus. One reason is the inability of the physician to fluoroscopically visually monitor the distal end of the basket assembly during the procedure such that the physician can best steer the basket assembly and attempt calculus entrapping. Further, the instruments of the prior art require that relatively complex mechanisms be built within the basket device to crush the calculi into smaller particles once captured or to obliterate the calculi altogether.